I can't believe that Maurice name Leon Spinks. Leon has very limited skills. He doesn't have fast hand or foot work, he doesn't have knock out power. Yet he defeated The Greatest and became undisputed heavyweight champion of the world. He was already over achieved with such limited skills. Now to answer the question. Mark Breland is the biggest under achiever. Mark was so dominant as an amateur that everyone was so sure that he will dominate the welterweight division when he turn pro. Some even said that because of his height he could move up and win the middleweight crown too. Well, Marlon Starlin, Aaron Davis and Jorge Vaca put him to sleep. Great boxer with good punching power but no chin.

Greg Page

Hector Camacho

Howard Davis Jr.

Ray Seales

Bernard Taylor

Meldrick Taylor.

Buster Douglas

Edwin Rosario

In no order sir:

Sam Langford -great overall skills, still no belt

Young Stribling - same as Sam

Paul Williams -good height, reach, had enough power, haven't used them well

Nikolai Valuev -Same as Paul

ZAb Judah -Good reflex, power and had to squander them

Jerry Quarry ,he was a very good heavyweight ,but overshadowed by some all time greats when he was in his prime ,Muhammad Ali ,Joe Frazier ,and George Foreman. If Jerry Quarry was around today he would probably be a major title holder.

Some of the son's of legenary boxer's suck as Joe Frazier and Tommy Hearns.

stevenson the cuban heavyweight that could never go pro but he won i dont know how many gold medals in several of the olympics he boxed in

freddie pendelton

frankie randall

mysterious billy smith

leon spinks